Thank you, gio. We turn to Oscar Pistorius. His murder trial, wrapping up with the defense preparing to put its final witnesses on the stand. And ABC's Matt Gutman is right there at the courthouse in south Africa, covering all of it. Good morning, Matt. Reporter: Good morning, Lara. That's right. The expert on the stand right now is supposed to be the defense's ace witness, blasting away at the assertion there was an argument between reeva and Oscar that's night. That's until the lead prosecutor began shooting him down, trying to discredit him. Setting up an elaborate display in court to do so. It was one of the most theatrical moments of the trial. The judge brought down to examine up close the bathroom. Using lasers and smoke, the prosecution trying to deflect the defense's claim of shoddy policework. The crime scene was absolutely not as it should have been. There was books taken out of the bookrack and put on to the blood. Reporter: That's the defense's ace witness, a top ballistics expert. He would physically re-enact the shooting. The first bullet hitting reeva's hip. The next one, in the arm. Collapse down, after the first shot. Reporter: Making the point that reeva wasn't in a defensive position when shot, suggesting there was no fiery argument between what was then south Africa's it couple before the shooting. Starting his testimony yesterday, he is a ballistic expert of seeming ly unassailable authority, until gerrie nel started questioning him. I think I answered the question. Reporter: Now known as the bull terrier, accusing him of consulting with Pistorius and burying an earlier report he compiled. Why would you not want us to see your earlier report? Reporter: He denied it, back pedaling, repeating, his memory had failed him. I can't remember the date, my lady. I can't remember. Reporter: Now, the defense has yet to explain why Oscar Pistorius fired into that door, knowing someone was behind it and knowing that it was illegal to do so. And time is running out for them. They only have a few witnesses left. But expect them to bring someone like a psychologist to the stand to explain Pistorius' frame of mind that night and maybe his sense of vulnerability.

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